Smoke or fire detection systems have been recognized as useful in enhancing the safety of occupants of large or multiple story buildings where egress from the building, in the event of a fire, might be difficult or dangerous. In such instances, it is desirable to be able to determine as early as possible that a fire or an alarm condition exists. One such system is disclosed in Teach et al. U.S. Pat. No. 4,916,432 assigned to the assignee hereof and incorporated herein by reference.
Counterbalancing the benefits of early detection is a need to guard against transient conditions or noise which might produce undesirable and unacceptable false alarms. For example, if some or all of the detectors are adjusted to have a high sensitivity, false alarms may be generated by electrical noise, cigarette or cooking smoke or the like.
Thus, there continues to be a need for detection or alarm systems which are highly sensitive but exhibit minimal false alarming in the presence of normally expected noise levels. It would be preferred if such systems could dynamically respond to both increasing and decreasing noise levels. Preferably, this result can be achieved without substantial additional expense in either new or existing systems.